Decoding inequality in years lived with disability: a cross-national age-based analysis from Sierra Leone, Burkina Faso, Burundi, and the Central African Republic

Age-based disparities in non-fatal health outcomes are critical yet underexplored in fragile sub-Saharan African settings, where communicable, maternal, perinatal, and nutritional conditions drive significant morbidity. This study quantifies age-specific inequalities in years lived with disability (YLDs) across Sierra Leone, Burkina Faso, Burundi, and the Central African Republic (CAR) to inform equitable health system planning. Using WHO Global Health Estimates (2021) accessed via the Health Equity Assessment Toolkit (HEAT, Version 6.0), we analyzed YLD rates per 100,000 population for communicable, maternal, perinatal, and nutritional conditions across 19 age groups. Standardized equity metrics: absolute difference (D), ratio (R), Slope Index of Inequality (SII), Relative Index of Inequality (RII), Population Attributable Risk (PAR), and Population Attributable Fraction (PAF) were applied to assess within-country disparities. Descriptive range measures were also calculated from the extracted estimates. National YLD rates varied from 2,163.0 (Burundi) to 3,143.6 (CAR) per 100,000. Age-specific rates followed a broadly U-shaped pattern, with the lowest rates at 15–19 years in all four countries and the highest rates in infants aged < 1 year in Sierra Leone (3,855.1) and Burkina Faso (5,030.3) and in adults aged 85 + years in Burundi (3,475.5) and CAR (5,550.9). Burkina Faso exhibited the steepest age gradient (D: 2,160.1; R: 1.8; SII: −3,094.0; 95% CI: −3,730.0 to − 2,460.0). In Burundi, the youngest and oldest age groups had almost identical rates (D: −41.2; R: 1.0), reflecting the symmetry of a U-shaped curve rather than a uniform distribution of burden (age-specific rates ranged from 1,597.2 to 3,475.5). CAR displayed a reversed end-to-end gradient (D: −721.6; R: 0.9), with older adults most affected. HEAT returned PAR and PAF values of 0.0 in all four countries, which were considered non-informative. The 95% confidence intervals of age-specific rates were wide and overlapped across age groups. Modeled age-specific YLD rates were highest in early childhood and, in Burundi and CAR, in the oldest age group, suggesting that age-responsive health planning may be warranted in fragile states. Single-gradient (SII, RII) and reference-based (PAR, PAF) measures summarized these U-shaped patterns poorly and should be interpreted alongside age-specific estimates. Integrating equity metrics into health planning could support progress towards Universal Health Coverage and Sustainable Development Goals (SDGs) 3 and 10.